1 April 2017

With no toothbrushes or toothpaste let alone dental floss or oral hygiene products, Neandertal teeth were plaque heaven, that’s the unsightly build up that makes teeth feel fuzzy to the tongue. Hardened plaque (dental calculus) is a goldmine for scientists who study human evolution. It “traps microorganisms that lived in the mouth and pathogens found in the respiratory and gastrointestinal tract, as well as bits of food stuck in the teeth, preserving the DNA for thousands of years,” says Dr Laura Weyrich, lead author of a new paper published in the journal Nature. “Genetic analysis of that DNA ‘locked-up’ in plaque, represents a unique window into Neandertal lifestyle, revealing what they ate, what their health was like and how the environment impacted their behaviour.” It also tells us they were locovores as well as omnivores.

An international team of researchers led by the University of Adelaide's Australian Centre for Ancient DNA (ACAD) and Dental School, with the University of Liverpool in the UK examined two Neanderthals from El Sidrón cave, Spain, and one from Spy cave in Belgium and found drastic differences in their diet that correlated with changes in their microbiomes. The samples range from 42,000 to around 50,000 years old.

“We found that the Neandertals from Spy Cave in Belgium (on the edge of a steppe-like environment of grassy hills and plains, populated with megafauna) consumed woolly rhinoceros and European wild sheep, supplemented with wild mushrooms. On the other hand those from El Sidrón Cave (in dense mountain forest) showed no evidence for meat consumption, but appeared instead to have a largely vegetarian diet, comprising pine nuts, moss, mushrooms and tree bark,” says Professor Alan Cooper, Director of ACAD.

“One of the most surprising finds, however, was in a Neandertal from El Sidrón, who suffered from a dental abscess visible on the jawbone. The plaque showed that he also had an intestinal parasite that causes acute diarrhoea, so clearly he was quite sick. He was eating poplar, which contains the pain killer salicylic acid (the active ingredient of aspirin), and we could also detect a natural antibiotic mould (Penicillium) not seen in the other specimens.”

“Apparently, Neandertals possessed a good knowledge of medicinal plants and their various anti-inflammatory and pain-relieving properties, and seem to be self-medicating. The use of antibiotics would be very surprising, as this is more than 40,000 years before we developed penicillin. Certainly, our findings contrast markedly with the rather simplistic view of our ancient relatives in popular imagination.”

Neandertals, ancient and modern humans also shared several disease-causing microbes, including the bacteria that cause dental caries and gum disease. The Neandertal plaque allowed reconstruction of the oldest microbial genome yet sequenced (Methanobrevibacter oralis), a commensal that can be associated with gum disease. Remarkably, the genome sequence suggests Neandertals and humans were swapping pathogens as recently as 180,000 years ago, long after the divergence of the two species.

The team also noted how rapidly the oral microbial community has altered in recent history. The composition of the oral bacterial population in Neandertals and both ancient and modern humans correlated closely with the amount of meat in the diet, with the Spanish Neandertals grouping with chimpanzees and our forager ancestors in Africa. In contrast, the Belgian Neandertal bacteria were similar to early hunter gatherers, and quite close to modern humans and early farmers.

“Not only can we now access direct evidence of what our ancestors were eating, but differences in diet and lifestyle also seem to be reflected in the commensal bacteria that lived in the mouths of both Neandertals and modern humans,” says Professor Keith Dobney, from the University of Liverpool.

“Major changes in what we eat have, however, significantly altered the balance of these microbial communities over thousands of years, which in turn continue to have fundamental consequences for our own health and well-being. This extraordinary window on the past is providing us with new ways to explore and understand our evolutionary history through the microorganisms that lived in us and with us.”